A conventional vehicle occupant weight sensing system senses the weight of the occupant and includes a weight sensor placed within the vehicle seat. Typically, the sensor is directly within the vertical load path of an occupant's weight and responds to the weight of the occupant on the seat.
In the art, a weight sensing system is often used in conjunction with a control system for controlling the deployment of an occupant protection device. One example type of an occupant protection device that may be controlled responsive to sensed weight is an inflatable occupant restraint device that includes an air bag. Upon the occurrence of a condition for which an occupant is to be protected, the restraint device is deployed and the air bag is inflated within an occupant compartment.
The art has recognized that it may be desirable to adjust deployment of the restraint device (e.g., modify inflation pressure of the air bag). Such a determination may be based, at least in part, on a condition of the occupant or object on the seat, such as the weight of the occupant or object on the seat. Air bag deployment control has accordingly developed wherein weight is considered as one of the deployment control conditions. Thus, methods and systems have been developed to control the deployment of air bags based, at least in part, on the weight of the occupant as sensed by a weight sensor.
For example, U.S. Pat. No. 5,413,378 to Steffens, Jr. et al., assigned to the assignee of the present invention, discloses a system for controlling an occupant restraint system. The system controls air bag deployment and includes a weight sensor for sensing the weight of the occupant. Deployment of the air bag is a function of the weight sensed by the weight sensor. More particularly, a controller establishes a weight range from the weight sensor. The controller controls air bag deployment by selecting one of a plurality of control zones which are dependant upon the sensed weight range.
Similarly, U.S. Pat. No. 5,906,393 to Mazur et al., also assigned to the assignee of the present invention, discloses an occupant restraint system and an associated control system for controlling the deployment of an air bag based, in part, upon a signal from a weight sensor that senses the weight of an occupant.
A seat belt is also commonly used as a component in a protection system. It is generally well known that a seat belt is used to fasten an occupant or a child seat into a vehicle seat. Depending on how tightly the seat belt is fastened across the occupant or child seat, the seat belt may exert a downward force upon the occupant or child seat. If sufficient, the magnitude of this downward force may be detectable by the weight sensor. As such, this downward force may affect the perceived weight of the occupant or object on the seat as sensed by the weight sensor.